6-Deoxyhexoses

Deoxyhexoses have not been found in bacterial polysaccharides, but there is one example of a 4-deoxyhexose, namely, 4-deoxy-D-arah//io-hex-ose. This sugar is a component of some 0-antigens from Citrobacter, for... 

Deoxy sugars 2-deoxy-araWno-hexose, 6-deoxyglucose and 2-deoxy-eo thro-pentose, fucose and rhamnose, 2-acetamido-2-deoxyhexoses ... 

The more-common 2-acetamido-2-deoxyhexoses have not been found as thymidine 5 -pyrophosphate derivatives. Nevertheless, the enzymic synthesis of thymidine 5 -(2-acetamido-2-deoxy-a-D-gluco-pyranosyl pyrophosphate) and -(2-acetamido-2-deoxy-a-D-galactopy-ranosyl pyrophosphate) has been achieved with enzyme preparations from Pseudomonas aeruginosa,116 Azotobacter vinelandii,52 and gastric mucosa.117... 

Other tetrahydroimidazoles have been obtained from the reaction of 2-amino-2-deoxyhexoses with isocyanates and with thiocyanates. Thus, 2-amino-2-deoxy-D-glucopyranose hydrochloride (78) reacts readily with phenyl isocyanate to yield77 the corresponding 4,5-D-glucopyrano-l-phenyl-4-imidazolidin-2-one (79). Alternatively, the tetraacetate 80 was converted into the urea derivative 81, the prod-... 

Oxazolidinones have been prepared by participation of an N-benzyloxycarbonyl group with a leaving group on126-131 C-l or C-3 of a 2-amino-2-deoxyhexose,132-134 such as 3,4,6-tri-0-acetyl-2-(benzyl-... 

The alkaline decomposition of 2-(N-nitroso)acetamido-2-deoxyhexoses provides a preparatively useful route to acetylenic sugar derivatives.217a,217b... 

It is possible to degrade 2-amino-2-deoxyhexoses to 2-amino-2-deoxy-pentoses by means of chain-shortening reactions from the nonreducing end of the molecule. Thus, Wolfrom and Anno38 converted ethyl 2-acetamido-2-deoxy-1 -thio-a-d-glucofuranoside (XV) into 2-amino-2-deoxy-a-D-xylose hydrochloride (XVI) by sequential application of periodate oxidation, borohydride reduction, and hydrolysis, as in the following reaction scheme. 

Whilst there appears to be limited scope at present for the utilization of these observations in determinations of polysaccharide structures, they can be of value when the Morgan-Elson test is applied to oligosaccharides containing amino sugar residues, as the work on the oligosaccharides from human milk2 has shown. Obviously, no simple relation exists between a positive test and the presence of free 2-acetamido-2-deoxyhexose, but much information may be culled by a consideration of all the factors outlined above. 

Equilibrium-dialysis experiments revealed two 2-acetamido-2-deoxy-D-galactose binding-sites per molecule of soybean agglutinin.544 This value was confirmed by gel filtration of the lectin on a column equilibrated with a radioactive ligand. The noninteracting, identical sites exhibited an association constant of Ka = 3.0 X 104 liter.mole-1 for this 2-acetamido-2-deoxyhexose. 

A color test described by Webb and Levy for 2-deoxy sugars was investigated further, and it was shown that, unlike 2-deoxypentoses and 2-deoxyhexoses, no reaction was obtained with a 2-deoxytetrose. However, the Webb-negative tyvelose and abequose, after periodate oxidation, gave a positive Webb test (as for 2-deoxypentoses), behavior which was consistent with their formulation as 3,6-dideoxyhexoses. ... 

Alcohol 470 was also converted to 3-deoxy-D-araZ m6>-heptulosonic acid [213b] and to enantio pure 2-deoxyhexoses [213c]. Cycloheptatrienone (tropone) has been converted into heptitol derivatives via the optical resolution of the (tropone)Fe(CO)3 complex [213d]. 

---